Permanent secretary Charan Phakdithanakul dropped the bombshell bribery allegation on Monday that a senior official tried to secure a not guilty verdict for the Thai Rak Thai Party by offering money to the judges.

He said two judges were offered the kickbacks to fix the verdict not to dissolve Thai Rak Thai but they refused to accept the bribes.

Charan refused to say if the two judges were from the Constitution Tribunal, Supreme or Administrative courts.

"My proof is solid because it is not just a statement but a hand-written letter. I want to show the letter but I have yet to ask for permission from the owners," Charan said.

He said the letter did not indicate a clear amount of money but it was written by hand and endorsed with signatures and a date.

Charan said bribery was a crime and the people who were offered kickbacks were the damaged party and could take legal action against the people who tried to bribe them.

Charan refused to name the official or the judges involved.

Tribunal judge Thanis Kesawapirak said on Monday he was unaware of any bribery attempt.

"The judge who said he knew knowing about the bribery has nothing to do with it or wasn't involved in the matter," Charan said.

Thanis voiced scepticism that any of the nine tribunal judges were offered kickbacks. He urged authorities to get to the bottom of the allegation in order to clear up any doubts about the judicial system.

Judicial Office deputy secretary-general Sarawut Benjathikul said offenders could be jailed for up to seven years and fined up to Bt14,000 for offering bribes.

Piyanuch Thamnukasetchai

The Nation